Field of the Invention
The present invention relates in general to the electrical connector field. More particularly, the present invention relates to providing a conductive path between two devices provided with electrical contacts distributed on a surface. Most particularly, the present invention relates to providing a solderless electrical interconnection between a first device and a second device, said first device comprising—but not limited to—a photonic package such as a Transmitter Optical Sub-Assembly (TOSA) and said second device comprising—but not limited to—a printed circuit board (PCB).
Background Art
Electrical connectors are in widespread use in the electronics industry. In many electronic and opto-electronic devices and systems a module such as a central processor unit (CPU), memory module, application-specific integrated circuit (ASIC) or optical and opto-electronic sub-assemblies (such as a TOSA), must be connected to a printed circuit board (PCB). In connecting such module to a PCB, a plurality of individual electrical contacts provided on the base of the module must be connected to a plurality of corresponding individual electrical contacts provided on the PCB surface. This set of contacts on the PCB dedicated to contacting the module contacts is known as a land grid array (LGA). Rather than permanently soldering the electronic module contacts to the LGA site, it is desirable to use connecting means that allow the module to be installed to and removed from the LGA site.
Interconnecting devices conjoined with LGA sites provide the user with the flexibility to upgrade or replace electronic modules during the manufacturing cycle and in the field. A trend in the electronics industry has been to increase both the quantity of lands in LGA sites and the density thereof, i.e., the number of contacts per unit area at the LGA site. Another trend in the electronics industry is to reduce the insertion force necessary to insert the electronic module into the LGA connector.
One type of LGA connector that has proven to be very reliable incorporates resilient wire bundles, which provide conductive paths between pads of two devices, such as a TOSA and a PCB or between two PCB's.
For example, U.S. Pat. No. 6,062,870 (Hopfer et al.)—ELECTRICAL INTERCONNECTS, discloses an electrical interposer that incorporates resilient wire bundles retained in holes of a flat carrier by compressive frictional engagement with a central section of the sidewall of each of the holes. In use, the carrier is placed between the two components to be interconnected—such as a PCB and a TOSA—and the resilient wire bundles provide conductive paths between the corresponding pads or lands of said components, which are held in an opposing relation. A problem with this device is that one or more of the resilient wire bundles may be jarred loose and fall out from the interposer during transit or handling, resulting in an open circuit between the two components. Another problem is that the resilient wire bundle, instead of being jarred completely out of the interposer, is only partially loose in such a way that, when compressed between the two components, the resilient wire bundle bends over and makes contact with an adjacent resilient wire bundle or an adjacent land, resulting in a short circuit.
US patent application No. 2004002233 (Advocate et al.)—METHOD OF ASSEMBLING AN INTERCONNECT DEVICE ASSEMBLY AND APPARATUS THEREFOR discloses a method of assembling an interconnect device assembly which consists of cylindrical resilient wire bundles captured with a carrier. The interconnect device assembly is placed in a fixture and the ends of the resilient wire bundles are deformed by shaping dies in the fixture so that the resilient wire bundles now have a dog bone shape. The dog bone shape of the resilient wire bundles prevents the resilient wire bundles from being partially or totally dislodged during handling and transit. However, one or more of the shaping dies may insufficiently deform the resilient wire bundle and thereby fail to prevent the same from being dislodged. Also, the shaping dies may inconsistently deform the resilient wire bundles (i.e., some shaping dies will under-penetrate the resilient wire bundles while other shaping dies will over-penetrate). The resulting unequal resilient wire bundle height increases the likelihood that one or more open circuits will occur when the resilient wire bundles are compressed between two electronic substrates.
US patent application No. 2008282539 (Brodsky et al.)—ELECTRICALLY CONNECTING TWO SUBSTRATES USING A RESILIENT WIRE BUNDLE CAPTURED IN AN APERTURE OF AN INTERPOSER BY A RETENTION MEMBER discloses a method and apparatus for electrically connecting two substrates using resilient wire bundles captured in apertures of an interposer by a retention film. The interposer comprises an electrically non-conductive carrier having two surfaces and apertures extending from surface to surface. A resilient wire bundle is disposed in each aperture. An electrically non-conductive retention film is associated with one or both surfaces of the carrier and has an orifice overlying each aperture. The width of each orifice is smaller than that of the underlying aperture to thereby enhance retention of the resilient wire bundle within the aperture. Pin contacts of one or both of the substrates make electrical contact with the resilient wire bundles by extending through the orifices of the retention film and partially through the apertures. In one embodiment, the interposer is a land grid array (LGA) connector that connects an electronic module and a printed circuit board (PCB). A problem with electrical connectors that incorporate resilient wire bundles is that the strands of the resilient wire bundles are not very robust. For example, the strands of resilient wire bundles are prone to spreading or “mushrooming” upon repeated insertions. If a resilient wire bundle is sufficiently mushroomed, an open circuit or near-open circuit will result when the mushroomed resilient wire bundle is subsequently compressed between two electronic substrates. This occurs because mushrooming can undesirably limit the compressive force on the resilient wire bundle and thereby increase electrical resistance through the resilient wire bundle to the point where an open circuit or near-open circuit is created. Moreover, the strands of resilient wire bundles can snag on mating features during insertion and withdrawals. If either a snagged strand of a resilient wire bundle or a mushroomed resilient wire bundle subsequently makes contact with an adjacent resilient wire bundle or an adjacent contact on the electronic substrate, a short circuit will result. Such a short circuit can catastrophically damage one or both of the electronic substrates being interconnected.
US patent application No. 2014342583 (McHugh)—LOW PROFILE ELECTRICAL CONNECTOR HAVE A FPC discloses a connector for electrically connecting a chip module to a PCB, comprising an insulative housing with a plurality of terminals therein, the insulative housing comprising a substrate and a sidewall extending upwardly, said substrate being provided with a plurality of through-holes and a flex film (FPC) located under the substrate, wherein the contact elements to the PCB pads consist of a plurality of solder balls fused into the bottom side of the vias of the FPC. One problem associated with this connector is the fact that it does not compensate for surface irregularities between the adjoined components. Moreover, the solder balls are subjected to distortion with repeated use of the connector, resulting in inadequate contacts between some balls and the pads, or even an open circuit.
It should therefore be apparent that a need exists for an enhanced assembly for connecting two substrates in a reliable way.